> Some people is doing 2 or 3 times the same image (RK05.png done 3 times by Fizbam).

Maybe if someone saves a second file for an image they have already completed, a nice message could pop up requesting that they select a different image? Like if XXXY saves a completed reading of image AA, and then tries to save a WIP in a different slot for image AA, a page could pop up saying something like "You have already submitted a reading of this image. It is key to the project that at least three different people submit readings of the image. You can best help us out by selecting a different image."

Same sort of thing could help prevent collisions. If XXXY has saved a WIP for image AA slot 1 and then YYYZ saves a WIP for the same image and slot, a message could pop up for YYYZ saying that XXXY appears to be working on the image, and to avoid duplication of work, would they please select another image.